May 29 (HealthDay News) -- Treatment with the anti-rejection drug sirolimus may lead to increased risk of diabetes in kidney transplant patients, say researchers who analyzed data on about 20,000 Medicare patients who had kidney transplants between 1995 and 2003.

None of the patients had diabetes before their kidney transplant. Compared to other anti-rejection drugs, sirolimus was associated with a 36 percent to 66 percent increased risk of diabetes after transplant.

"We demonstrated a robust association between sirolimus and diabetes after transplantation in a large group of kidney transplant recipients in the United States. The risk of diabetes was independent of other factors that are known to increase the risk of diabetes," Dr. John S. Gill, of the University of British Columbia in Vancouver, Canada, said in a prepared statement.

The study was expected to be published in the July issue of the Journal of the American Society of Nephrology.

"Sirolimus is a newer type of anti-rejection drug that has not been associated with diabetes in transplant recipients. However, a number of animal studies and small clinical studies have suggested that sirolimus may increase the risk of diabetes," Gill noted.

This is the first large clinical study to suggest this association and indicates that more research is needed "to further clarify that risk of diabetes in sirolimus-treated patients."

Diabetes is a serious and increasingly common complication following kidney transplantation. Risk factors include age, race/ethnicity and obesity.

"Patients who develop diabetes after transplantation have roughly the same risk of transplant failure as patients who develop acute transplant rejection," Gill said.

SOURCE: American Society of Nephrology, news release, May 22, 2008